Duty ratio corrector, and memory device having the same

ABSTRACT

The present invention discloses a duty ratio corrector which can reduce power consumption by blocking current paths between output terminals and a ground terminal by applying input signals for turning off switching devices for generating an auxiliary voltage for correcting a duty ratio at an initial stage, and which can improve an operational speed by changing the auxiliary voltage from a predetermined voltage, not 0V, to an target voltage, and a memory device having the same.

This application relies for priority upon Korean Patent Application No.2004-0027096 filed on Apr. 20, 2004, the contents of which are hereinincorporated by reference in their entirety.

BACKGROUND

1. Field of the Invention

The present invention relates to a duty ratio corrector and a memorydevice having the same, and more particularly to, a duty ratio correctorwhich can minimize power consumption and rapidly generate an outputsignal by blocking current paths in an initial mode, and a memory devicehaving the same.

2. Discussion of Related Art

All memory devices use clock signals. As an operational speed of thememory device increases, a duty ratio of an input clock signalinfluences performance of the whole chip. Therefore, a duty ratiocorrector for maintaining a duty ratio of a clock signal at 50% has beenemployed.

The operation of the duty ratio corrector will now be described.

FIG. 1 is a concept diagram for explaining the operation of the generalduty ratio corrector.

Referring to FIG. 1, the duty ratio corrector basically includes tworesistance devices R101 and R102, two switching devices N101 and N102, acurrent supply means I101 and two capacitors C101 and C102. The couplingstructure of the duty ratio corrector will now be explained in moredetail.

The first resistance device R101 is coupled between a power voltageterminal VDD and a first output terminal OUT1. The second resistancedevice R102 is coupled between the power voltage terminal VDD and asecond output terminal OUT2. Here, the first and second resistancedevices R101 and R102 have the same resistance value.

The first switching device N101 is coupled to the first resistancedevice R101 and operated according to an inverted clock signal clkb. Thesecond switching device N102 is coupled to the second resistance deviceR102 and operated according to a clock signal clk.

The current supply means I101 is coupled between the first and secondswitching devices N101 and N102 and a ground terminal GND, so that aconstant current can regularly flow through the first and secondresistance devices R101 and R102.

The first capacitor C101 is coupled between the first output terminalOUT1 and the ground terminal GND. When the first switching device N101is turned on, the first capacitor C101 is charged or discharged by thecurrent flowing through the first resistance device R101 by the currentsupply means I101. The second capacitor C102 is coupled between thesecond output terminal OUT2 and the ground terminal GND. When the secondswitching device N102 is turned on, the second capacitor C102 is chargedor discharged by the current flowing through the second resistancedevice R102 by the current supply means I101.

The operation of the duty ratio corrector will now be described.

FIGS. 2A to 2E are waveform diagrams for explaining the operation of theduty ratio corrector of FIG. 1.

As shown in FIG. 2A, when the clock signal clk is inputted in a higherlevel than a reference voltage Vref for deciding a high level and a lowlevel and when the inverted clock signal clkb is inputted in a lowerlevel than the reference voltage Vref, as shown in FIG. 2B, a rate of ahigh level pulse to a low level pulse of a clock pulse clkp or aninverted clock pulse clkpb is changed. In this case, an operationalmargin is sufficient in a high level but deficient in a low level, togenerate errors.

When receiving the clock signals clk and clkb, the duty ratio correctorincreases the level of the clock signal clk and decreases the level ofthe inverted clock signal clkb, thereby correcting the rate of the highto low level. This operation will now be explained in more detail.

When the inverted clock signal clkb is inputted to the first switchingdevice N101 in a high level, a turn-on time of the first switchingdevice N101 gets longer than a turn-off time thereof. Accordingly, atime of flowing the current through the first resistance device R101 isrelatively long, and thus the first capacitor C101 is more charged thandischarged. As depicted in FIG. 2C, a level of a first auxiliary voltageDCC outputted to the first output terminal OUT1 gradually increases. Thefirst auxiliary voltage DCC is added to the inverted clock signal clkb,and thus the level of the inverted clock signal clkb increases as shownin FIG. 2D.

On the other hand, when the clock signal clk is inputted to the secondswitching device N102 in a low level, a turn-off time of the secondswitching device N102 gets longer than a turn-on time thereof.Accordingly, a time of flowing the current through the second resistancedevice R102 is relatively short, and thus the second capacitor C102 ismore discharged than charged. As depicted in FIG. 2C, a level of asecond auxiliary voltage DCCB outputted to the second output terminalOUT2 gradually decreases. The second auxiliary voltage DCCB is added tothe clock signal clk, and thus the level of the clock signal clkdecreases as shown in FIG. 2D.

When the level of the clock signal clk decreases and the level of theinverted clock signal clkb increases by the above operation, as shown inFIG. 2E, an intermediate level between the clock signal clk and theinverted clock signal clkb is identical to the level of the referencevoltage Vref, and thus the rate of the high to low level is the same.

As described above, the duty ratio corrector is operated according tothe clock signal clk and the inverted clock signal clkb which haveopposite phases. When receiving the opposite phase signals at the sametime, any one of the first switching device N101 and the secondswitching device N102 must be turned on. Therefore, the current startsto flow in a standby mode or before a normal operation mode, whichresults in high power consumption.

In addition, when one of the first switching device N101 and the secondswitching device N102 is turned on, any one of the first auxiliaryvoltage DCC and the second auxiliary voltage DCCB is outputted as 0V. Inorder to perform a normal operation, 0V of auxiliary voltage DCC or DCCBmust be increased to an target level. However, it takes a long time toincrease the auxiliary voltage DCC or DCCB to the target level, and thustakes a long time to correct the duty ratio. As a result, it influencesa lock time of a delay locked loop using the same.

SUMMARY OF THE INVENTION

The present invention is directed to a duty ratio corrector which canreduce power consumption by blocking current paths between outputterminals and a ground terminal by applying input signals for turningoff switching devices for generating an auxiliary voltage for correctinga duty ratio at an initial stage, and which can improve an operationalspeed by changing the auxiliary voltage from a predetermined voltage,not 0V, to an target voltage, and a memory device having the same.

One aspect of the present invention is to provide a duty ratio correctorhaving first and second switching devices for generating an auxiliaryvoltage for correcting a rate of a high to low level of a clock signal,and controlling a current path from a power voltage terminal to a groundterminal according to first and second input signals having oppositephases, the duty ratio corrector including: a first input signal controlunit for turning off the first switching device by blocking the firstinput signal in a standby mode according to a reset signal; and a secondinput signal control unit for turning off the second switching device byblocking the second input signal in the standby mode according to thereset signal, whereby the current path is blocked in the standby mode,and an output signal is outputted in a higher voltage than 0V.

According to another aspect of the present invention, a duty ratiocorrector includes: a first resistance device coupled between a powervoltage terminal and a first output terminal; a second resistance devicecoupled between the power voltage terminal and a second output terminal;a first capacitor coupled between the first output terminal and a groundterminal; a second capacitor coupled between the second output terminaland the ground terminal; a first switching device for controlling acurrent path from the first resistance device to the ground terminalaccording to a first input signal; a second switching device forcontrolling a current path from the second resistance device to theground terminal according to a second input signal having the oppositephase to that of the first input signal; a first input signal controlunit for turning off the first switching device by blocking the firstinput signal in a standby mode according to a reset signal; and a secondinput signal control unit for turning off the second switching device byblocking the second input signal in the standby mode according to thereset signal.

Preferably, the first input signal control unit includes: a NAND gatefor receiving the reset signal and the first input signal; and aninverter for inverting the output signal from the NAND gate.

Preferably, the second input signal control unit includes: a NAND gatefor receiving the reset signal and the second input signal; and aninverter for inverting the output signal from the NAND gate.

According to yet another aspect of the present invention, a memorydevice having a duty ratio corrector includes: a duty ratio correctorfor generating an auxiliary voltage for correcting a rate of a high tolow level of a pulse signal by repeatedly charging and discharging acurrent by a switching operation, switching devices of which beingoperated according to a first input signal and a second input signalhaving opposite phases; and a buffer for buffering the first inputsignal and the second input signal, supplying the buffered signals tothe duty ratio corrector, and outputting the first and second inputsignals for turning off the switching devices in a standby modeaccording to a reset signal.

Preferably, the buffer includes: a first NAND gate for receiving thereset signal and the first input signal; a first inverter for outputtingthe first input signal by inverting the output signal from the firstNAND gate; a second NAND gate for receiving the reset signal and thesecond input signal; and a second inverter for outputting the secondinput signal by inverting the output signal from the second NAND gate.

According to yet another aspect of the present invention, a memorydevice having a duty ratio corrector includes: a duty ratio correctorfor generating an auxiliary voltage for correcting a rate of a high tolow level of a pulse signal by repeatedly charging and discharging acurrent by a switching operation, switching devices of which beingoperated according to a first input signal and a second input signalhaving opposite phases; and a phase separator for generating the firstinput signal and the second input signal as input signals, andoutputting the first and second input signals for turning off theswitching devices in a standby mode according to a reset signal.

Preferably, the phase separator includes: a first NAND gate forreceiving the reset signal and the input signal; a first inverter foroutputting the first input signal by inverting the output signal fromthe first NAND gate; a second inverter for inverting the input signal; asecond NAND gate for receiving the reset signal and the output signalfrom the second inverter; and a third inverter for outputting the secondinput signal by inverting the output signal from the second NAND gate.

Preferably, a capacitor is further installed between an output terminalof the first NAND gate and a ground terminal, for equalizing delay ofthe first input signal and the second input signal.

Preferably, a transistor being coupled between an output terminal of thesecond inverter and the ground terminal and having its gate coupled toan input terminal of the second inverter is further installed to improvean operational speed of the second inverter.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention may be had byreference to the following description when taken in conjunction withthe accompanying drawings in which:

FIG. 1 is a concept diagram for explaining an operation of a generalduty ratio corrector;

FIGS. 2A to 2E are waveform diagrams for explaining the operation of theduty ratio corrector of FIG. 1;

FIG. 3 is a circuit diagram illustrating a duty ratio corrector inaccordance with a preferred embodiment of the present invention;

FIG. 4 is a circuit diagram illustrating a memory device having a dutyratio corrector in accordance with a first embodiment of the presentinvention; and

FIG. 5 is a circuit diagram illustrating a memory device having a dutyratio corrector in accordance with a second embodiment of the presentinvention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

A duty ratio corrector and a memory device having the same in accordancewith preferred embodiments of the present invention will now bedescribed in detail with reference to the accompanying drawings.Wherever possible, the same reference numerals will be used throughoutthe drawings and the description to refer to the same or like parts.

FIG. 3 is a circuit diagram illustrating a duty ratio corrector inaccordance with a preferred embodiment of the present invention.

As illustrated in FIG. 3, the duty ratio corrector basically includestwo resistance devices R301 and R302, two switching devices S301 andS302, a current supply means 301 and two capacitors C301 and C302, andfurther includes input signal control units 310 and 320. The couplingstructure of the duty ratio corrector will now be explained in moredetail.

The first resistance device R301 is coupled between a power voltageterminal VDD and a first output terminal OUT1. The second resistancedevice R302 is coupled between the power voltage terminal VDD and asecond output terminal OUT2. Here, the first and second resistancedevices R301 and R302 have the same resistance value.

The first switching device S301 is coupled to the first resistancedevice R301 and operated according to an inverted clock signal clkb. Thesecond switching device S302 is coupled to the second resistance deviceR302 and operated according to a clock signal clk. Here, the first andsecond switching devices S301 and S302 can be designed to have impedancevalues. In this case, when the switching device is turned on, an initiallevel of an auxiliary voltage is changed due to voltage distributionwith the resistance device coupled in series to the switching device.

The current supply means 301 is coupled between the first and secondswitching devices S301 and S302 and a ground terminal GND, so that aconstant current can regularly flow through the first and secondresistance devices R301 and R302. The current supply means 301 can beselectively omitted. When the current supply means 301 is not used, thefirst switching device S301 is coupled between the first resistancedevice R301 and the ground terminal GND, and the second switching deviceS302 is coupled between the second resistance device R302 and the groundterminal GND.

The first capacitor C301 is coupled between the first output terminalOUT1 and the ground terminal GND. When the first switching device S301is turned on, the first capacitor C301 is charged or discharged by thecurrent flowing through the first resistance device R301 by the currentsupply means 301. The second capacitor C302 is coupled between thesecond output terminal OUT2 and the ground terminal GND. When the secondswitching device S302 is turned on, the second capacitor C302 is chargedor discharged by the current flowing through the second resistancedevice R302 by the current supply means 301.

On the other hand, when the duty ratio corrector is not operated, thefirst input signal control unit 310 prevents the inverted clock signalclkb from being transmitted to the first switching device S301 accordingto a reset signal reset. The first input signal control unit 310includes a NAND gate N301 for receiving the inverted clock signal clkband the reset signal reset, and an inverter I301 for transmitting theinverted clock signal clkb to the first switching device S301 byinverting the output signal from the NAND gate N301.

When the duty ratio corrector is not operated, the second input signalcontrol unit 320 prevents the clock signal clk from being transmitted tothe second switching device S302 according to the reset signal reset.The second input signal control unit 320 includes a NAND gate N302 forreceiving the clock signal clk and the reset signal reset, and aninverter I302 for transmitting the clock signal clk to the secondswitching device S302 by inverting the output signal from the NAND gateN302.

In accordance with the present invention, the duty ratio corrector canreduce power consumption by blocking current paths between the outputterminals OUT1 and OUT2 and the ground terminal GND by turning off theswitching devices S301 and S302 for generating an auxiliary voltage DCCor DCCB at an initial stage by the first and second input signal controlunits 310 and 320, and can improve an operational speed by changing theauxiliary voltage DCC or DCCB from a predetermined voltage, not 0V, toan target voltage.

Here, an intermediate voltage between the first auxiliary voltage DCCand the second auxiliary voltage DCCB is determined by distributing thepower voltage VDD according to the impedance values of the resistancedevices and the switching devices. The level of the first auxiliaryvoltage DCC and the level of the second auxiliary voltage DCCB can becontrolled by correcting the resistance rate thereof, and thus rise orfall of the clock signal clk and the inverted clock signal clkb can alsobe controlled.

On the other hand, the input signals of the duty ratio corrector areinputted through a phase separator or buffer. When the duty ratiocorrector is not operated, the phase separator or buffer can output theinput signals according to the reset signal, so that the switchingdevices for generating the auxiliary voltage can be turned off at aninitial stage.

FIG. 4 is a circuit diagram illustrating a memory device having a dutyratio corrector in accordance with a first embodiment of the presentinvention.

Referring to FIG. 4, when an input signal is one signal such as a clocksignal, the memory device includes a phase separator 410 and a dutyratio corrector 420.

The phase separator 410 is divided into a first output unit 411 and asecond output unit 412.

The first output unit 411 includes a NAND gate N401 for receiving areset signal reset for deciding an operation or non-operation of theduty ratio corrector 420 and a clock signal clkin, and an inverter I401for outputting a clock signal clk by inverting the output signal fromthe NAND gate N401. Here, a capacitor C401 can be additionally installedbetween an output terminal of the NAND gate N401 and a ground terminal,for equalizing delay of the clock signal clk and an inverted clocksignal clkb generated in the second output unit 412. Accordingly, thefirst output unit 401 outputs the clock signal clk according to thereset signal reset only when the duty ratio corrector 420 is operated,and outputs a low level signal when the duty ratio corrector 420 is notoperated.

The second output unit 412 includes a first inverter I402 for invertingthe clock signal clkin, a NAND gate N402 for receiving the reset signalreset for deciding the operation or non-operation of the duty ratiocorrector 420 and the output signal from the first inverter I402, and asecond inverter I403 for outputting the inverted clock signal clkb byinverting the output signal from the NAND gate N402. Here, a transistorT401 being coupled between an output terminal of the first inverter I402and the ground terminal and having its gate coupled to an input terminalof the second inverter I402 can be additionally installed to equalizedelay of the inverted clock signal clkb and the clock signal clkgenerated in the first output unit 411 and improve an operational speedby increasing current paths. Therefore, the second output unit 402outputs the inverted clock signal clkb according to the reset signalreset only when the duty ratio corrector 420 is operated, and outputs alow level signal when the duty ratio corrector 420 is not operated.

The clock signal clk and the inverted clock signal clkb from the phaseseparator 410 are transmitted respectively to a first switching device(N101 of FIG. 1) and a second switching device (N102 of FIG. 1) of theduty ratio corrector 420, for reducing power consumption by blockingcurrent paths between output terminals OUT1 and OUT2 and the groundterminal when the duty ratio corrector 420 is not operated, andimproving an operational speed by changing an auxiliary voltage DCC orDCCB from a predetermined voltage, not 0V, to an target voltage.

FIG. 5 is a circuit diagram illustrating a memory device having a dutyratio corrector in accordance with a second embodiment of the presentinvention.

As illustrated in FIG. 5, when input signals are two signals inp and innhaving different phases, the memory device includes a buffer 510 and aduty ratio corrector 520.

The buffer 510 includes a first NAND gate N501 for receiving a resetsignal reset for deciding an operation or non-operation of the dutyratio corrector 520 and the first input signal inp, a first inverterI501 for outputting a clock signal clk by inverting the output signalfrom the first NAND gate N501, a second NAND gate N502 for receiving thereset signal reset and the second input signal inn, and a secondinverter I502 for outputting an inverted clock signal clkb by invertingthe output signal from the second NAND gate N502.

Accordingly, the buffer 510 outputs the clock signal clk and theinverted clock signal clkb according to the reset signal reset only whenthe duty ratio corrector 520 is operated, and outputs a low level signalwhen the duty ratio corrector 520 is not operated.

The clock signal clk and the inverted clock signal clkb from the buffer510 are transmitted respectively to a first switching device (N101 ofFIG. 1) and a second switching device (N102 of FIG. 1) of the duty ratiocorrector 520, for reducing power consumption by blocking current pathsbetween output terminals OUT1 and OUT2 and a ground terminal when theduty ratio corrector 520 is not operated, and improving the operationalspeed by changing an auxiliary voltage DCC or DCCB from a predeterminedvoltage, not 0V, to an target voltage.

As discussed earlier, in accordance with the present invention, the dutyratio corrector and the memory device having the same can reduce powerconsumption by blocking the current paths between the output terminalsand the ground terminal by applying the input signals for turning offthe switching devices for generating the auxiliary voltage forcorrecting the duty ratio at an initial stage, and can improve theoperational speed by changing the auxiliary voltage from a predeterminedvoltage, not 0V, to the target voltage.

Although the present invention has been described in connection with theembodiment of the present invention illustrated in the accompanyingdrawings, it is not limited thereto. It will be apparent to thoseskilled in the art that various substitutions, modifications and changesmay be made thereto without departing from the scope and spirit of theinvention.

1. A duty ratio corrector including first and second switching devicesfor generating an auxiliary voltage for correcting a rate of a high tolow level of a clock signal, and controlling a current path from a powervoltage terminal to a ground terminal according to first and secondinput signals having opposite phases, the duty ratio correctorcomprising: a first input signal control unit for turning off the firstswitching device by blocking the first input signal in a standby modeaccording to a reset signal; and a second input signal control unit forturning off the second switching device by blocking the second inputsignal in the standby mode according to the reset signal, whereby thecurrent path is blocked in the standby mode, and an output signal isoutputted in a higher voltage than 0V.
 2. The duty ratio corrector ofclaim 1, wherein the first input signal control unit includes: a NANDgate for receiving the reset signal and the first input signal; and aninverter for inverting the output signal from the NAND gate.
 3. The dutyratio corrector of claim 1, wherein the second input signal control unitincludes: a NAND gate for receiving the reset signal and the secondinput signal; and an inverter for inverting the output signal from theNAND gate.
 4. A duty ratio corrector, comprising: a first resistancedevice coupled between a power voltage terminal and a first outputterminal; a second resistance device coupled between the power voltageterminal and a second output terminal; a first capacitor coupled betweenthe first output terminal and a ground terminal; a second capacitorcoupled between the second output terminal and the ground terminal; afirst switching device for controlling a current path from the firstresistance device to the ground terminal according to a first inputsignal; a second switching device for controlling a current path fromthe second resistance device to the ground terminal according to asecond input signal having the opposite phase to that of the first inputsignal; a first input signal control unit for turning off the firstswitching device by blocking the first input signal in a standby modeaccording to a reset signal; and a second input signal control unit forturning off the second switching device by blocking the second inputsignal in the standby mode according to the reset signal.
 5. The dutyratio corrector of claim 4, wherein the first input signal control unitcomprises: a NAND gate for receiving the reset signal and the firstinput signal; and an inverter for inverting the output signal from theNAND gate.
 6. The duty ratio corrector of claim 4, wherein the secondinput signal control unit comprises: a NAND gate for receiving the resetsignal and the second input signal; and an inverter for inverting theoutput signal from the NAND gate.